Search Documents

By A. A. Nourbakhsha

The main application of refractories based on andalusite in ferrous metallurgy are in air heaters of blast furnaces, mobile mixers, and hot-metal transfer, pig iron ladle, steel-casting, and intermediate ladles. Three specific properties of andalusite are very interesting for the production of high-quality shaped and unshaped mullite refractories: being free of water, its crystal a remains stable without changing its density or volume after firing and therefore has no internal porosity .Graphite additives due to its great wetting ability play an important role in raising the property of refractory bodies. In order to improve properties of andalusite graphite bodies, oxidant agent for increasing in hot strength and oxidation resistance can not be avoided. In this research, firstly 8 pig iron ladles from ESC(esfahan Steel company) with different conditions selected and monitored during usage to determine of main factors affecting on corrosion of refractories. Results showed that tap to tap time, undischarged pig iron ,penetrated pig iron are the main ones.Literature studies showed that the graphite addition help to thermal shock resistance and liquid penetration(steel,pig iron) effect. In this research particle size distribution of aggregates containing andalusite and graphite determined by andreazen equation. Then different mixes with different percentage of graphite,Si, FeSi, SiC prepared by uniaxially pressing under 1500kgf/cm2 pressure by adding 4%wt novalak resin and 0.4%wt HMTA as hardner. Samples fired at 1100-1500oC under reduction atmosphere. According to specific standards density, porosity and CCS measured. Analytical tests such as XRD, SEM were carried out on sample selected from point of view of mechanical properties at different temperatures. Results showed that optimized amount of Si and Fe-Si for _-SiC formation in body is 4 and 6 %wt respectively at 1500OC. XRD and SEM analysis on sample with Fe-Si additives showed no destructive phase through the matrix, also SiC additives not only increase oxidation resistance but also no effect on thermo-mechanical properties.

Oct 1, 2011

Everybody would agree that a good roadway leads to more efficient haulages by reducing haul times, smoother and safer operation for operator and less wear and tear on tires and equipment, thus improving availability and overall costs efficiency. There is a number of factors that come into play to achieve this especially when developing a mine. Excavations of Ramps and Headings: Operators should follow surveyors and layouts accurately while driving ramps. To maintain constant grades on ramps, which leads to better design control of water and easier grading of roadways. Dips and dives lead to needless over excavations and unnecessary cost and disposal of waste rock. When dressing a ramp some areas may require 2 to 3 feet of material to correct the dips and perfect to constant grade. You may ask yourself, is this all necessary? A small exercise is to follow a loaded haulage truck up ramp. At the first hump, grade change, notice the down shift and notice how far the truck travels to regain the up shift and his speed. The difference is remarkably noticeable when the grade is constant. All this leads to less driveline shock, less horsepower demand, better fuel efficiency and more productivity. Drill & Blast Patterns to control water for Ramp Headings: The drill pattern needs to allow for a ditch. A slight cross fall to form a ditch can easily be done with the lifters. The preferred side of the ditch is always the inside curve of the ramp as it has less tendency to erode roadbed material. On a level, the ditch is dictated by the sump location. A blasted ditch will eliminate water pounding and keep the roadbed dry. Water trapped in roadbed is the major cause of rollout and de-stability of roadbed. If the water is allowed to drain in the middle of the ramp it will cause erosion, movement and loss of fines and an increase in grading intervals.

Feb 1, 2008

By A. Fyson, M. P. Smith, Margarete Kalin

"Drums containing 0.07 m3 of pyritic waste rock from a zinc/copper mine, with and without Natural Phosphate Rock (NPR) additions (40 kg/t waste rock) were set up outdoors. The effluent chemistry has been monitored over a period of 709 days. In the presence of NPR, the cumulative acidity discharged from 7 out of 8 drums was 80 % less than that discharged from drums without NPR. Mixing NPR throughout the drums was more effective in reducing acidity than placement of the NPR in a layer in the drum. NPR treatment was more effective for 'fresh' waste rock than for material which had weathered for more than 4 years. It is concluded that application of NPR to pyritic waste rock could greatly reduce acidity generated.IntroductionWaste rock dumps are significant sources of acid, generated by the oxidation of sulphides. Oxygen and water supply are oxidation rate-controlling factors, and oxygen supply is the reaction-limiting component. If secondary minerals can be formed on the surface of the rocks, pyrite oxidation and therefore acid generation may be reduced or inhibited. Neutralizing agents such as limestone do not prevent the oxidation of pyrite but treat the resultant acid mine drainage (AMD) or acid rock drainage (ARD).Meek et al. (1991) determined in pilot scale experiments that apatite mixed with tailings was more cost effective than liming or use of PVC liners to reduce oxygen and water penetration into the tailings. Phosphate is not acting as a neutralising agent but it creates a chemical condition on pyritic surfaces which prevents reactions of the oxidising agents. Precipitation of principally iron phosphates physically isolates the pyrite surfaces from further oxidation (Ziemkiewicz 1990; Evangelou 1994). The chemistry of the phosphate effects has been described by Spotts and Dollhopf (1990). Secondary mineral formation was evident in the leach pile at Gibraltar when leaching was impaired (Scott, 1991) indicating a link between oxidation and the mineral-formation process. This paper reports on effluent characteristics when waste rock is generating acid in the presence of NPR."

Jan 1, 1995

By J. R. Johanson, A. W. Jenike

"A solid flows out of a bin provided that the outlet is sufficiently large so that stable obstructions to flow do not develop. The geometry and surface finish of a bin and the construction of the feeder determine the type of flow pattern which then develops within the bin. The pattern, in turn, affects the uniformity and consistency of the stream, segregation, caking, degradation, live capacity and the action of level measuring devices.In most bins now in operation, material flows toward the feeder through a channel which forms within the stationary solid. This is referred to as funnel flow. If the hopper of the bin is sufficiently steep and smooth and the feeder capable of drawing material across the whole area of the outlet, all the solid flows whenever the feeder is in operation; this is referred to as mass flow. Mass-flow bins are usually far superior to funnel-flow bins; their initial cost is also usually higher.The paper describes the design criteria used in deter-mining the minimum bin outlet needed for flow and the bin geometry needed for mass flow."

Jan 1, 1970

By A. D. McKay

Uranium exploration expenditure in Australia reached a record level of A$220.5 million in 2008, which has subsequently declined to A$185.2 million for the year ended 30 June 2009. Recent discoveries include: Ranger 3 Deeps east of Ranger open pit (Northern Territory), Pepegoona and Yadglin sandstone hosted deposits (South Australia), and Thunderball project (Northern Territory). Australia?s Reasonably Assured Resources recoverable at costs of <US$80/kg U at June 2009 are estimated to be 1,210,000 t U, 4% higher than the estimate for December 2008. The main additions were in the south eastern portion of the Olympic Dam orebody. The Olympic Dam Expansion is based on a large open pit and will increase output to an annual capacity of 19,000 t U3O8; 750,000 t copper; 800,000 ounces gold. The Four Mile in situ recovery project was approved in July 2009. An ion exchange facility is to be constructed at Four Mile and uranium-bearing resins will be transported to the Beverley plant to recover the uranium. Recent developments at Ranger mine, and Honeymoon, Oban and Yeelirrie projects are discussed.

Aug 1, 2010

Polymer electrolyte membrane (PEM) fuel cell has increasingly become the potential choice of zero-emission power source for portable, mobile and stationary co¬generation applications. However, technical barriers need to be overcome before its widespread commercialization; cost reduction and performance improvement including reliability are the two key areas, that can be realized through better cell/stack design and improved understanding of the transport processes occurring inside the individual cells and stacks. In this presentation, we will provide an overview of various cell/stack models that are available in the literature, their strength and weakness, and then present a comprehensive multi-species, multi-phase and multi-dimensional formulation of a single PEM fuel cell, with consistent and systematic formulation for all the regions involved, including the solid bipolar plates, gas flow channels, the electrode backing layers, the catalyst layers and the electrolyte membrane. Such a detailed approach allows us to extract sufficient information to the analysis of a stack of PEM fuel cells. Stack model will be presented that investigates the various stack designs and flow configurations, and the optimal stack design based on the present study will be described. Also some innovative cell/stack designs will be featured.

Jan 1, 2005

By Aimee Williamson

Bio-mining is a cost-effective, energy efficient and potentially environmentally protective method of exploiting a variety of ore deposits, from high-grade base metal deposits of nickel to lower-grade uranium deposits such as are found in the uraniferous quartz-pebble conglomerate beds of the Quirke Syncline, Elliot Lake, Ontario, using bacterial metabolic processes are used to enhance the solubilization of the metal(s) of interest. The cost effectiveness of bio-mining in Elliot Lake depends on the bacterially-influenced dissolution metals of economic importance, as well as on the ability to suppress microbiological activity following the release to solution of the economically important elements. This poster provides an overview of elemental recovery results and release kinetics for more than 50 elements. The data is obtained using a combination of advanced spectroscopic tools (ICPAES and ICP-MS) to analyze solutions obtained from a series of environmentally controlled biologically mediated uranium ore extraction experiments. The focus will be on rare earth elements, potential environmentally toxic elements, and metals of economic importance. Furthermore, the importance of these findings will be put into an economic and geologic context for the re-development of the mining industry of the Elliot Lake Camp.

Aug 1, 2010

By K. Murase

Potentiostatic electrodeposition behavior of dendritic copper from acidic copper(I) chloride (cuprous chloride) baths containing sodium chloride and sodium bromide was investigated. The morphology, or appearance, of copper dendrite and the sodium content in the dendrite as an impurity were both influenced by deposition potential (0 to ?150 mV vs. SHE) and bath temperature (R.T. to 60 C), while the current efficiency for the deposition was 99% or more irrespective of the deposition conditions examined. The bath pH did not affect the deposition behavior in the pH range of 0 to 2. Bath temperature was found to be the most important factor influencing the deposition current. The current density of the dendrite deposition on a titanium cathode was lower than that onto a copper cathode with the same substrate surface area. The reproducibility of the current for the dendrite deposition was poorer when an as-polished titanium cathode was used, although it was improved by surface treatment of the cathode with an HF-HNO3-H3PO4 solution before electrodeposition. The deposition behaviors were discussed with the potential-pH diagram of the Cu-Cl-H2O system.

Jan 1, 2007

By M. Lundström

The Outotec HydroCopper® process is a novel technology, developed and registered by Outotec Technology Oy, for leaching copper from chalcopyrite using cupric chloride solution. The leaching process is operated at atmospheric pressure in a stirred tank reactor, at temperatures near the boiling point of water and pH values between 1.5 and 2.5. During the leaching of chalcopyrite in cupric chloride solution, a reaction product layer forms on the mineral surface. In the present work, the formation and the composition of the reaction product layer was studied in an environment similar to that of the HydroCopper® process. The effect of the process parameters on the reaction product layer was investigated. Electrochemical measurements, including A.C. impedance spectroscopy and microscopic observations were carried out and an equivalent circuit was used to determine the surface parameters, such as the reaction product layer capacitance and the charge transfer resistance. The results suggest that, at low pH, a passivating sulfur-rich layer forms, whereas at high pH, a more porous iron-rich layer was detected. The values measured can give useful information for optimising the leaching parameters of the HydroCopper® process. Cu2007

Jan 1, 2007

By H. Saari, M. Pates, P. C. Patnaik, A. Merati

Single crystal nickel-base superalloys such as PWA1484 exhibit superior performance compared to conventional superalloys, and are used extensively in turbine blade applications requiring good high temperature properties. The life of these blades is typically limited by cracks and erosion. Due to the high cost of these blades, welding techniques are being considered to weld/repair worn components, extending their useful lives and delaying the need for expensive replacement components. However, the sensitivities for solidification cracking and post weld heat treatment cracking are relatively high in these alloys. Electron beam (EB) welding can deliver concentrated heat sources and has the potential to address these issues. Numerous welding trials and structural tests must be conducted to identify the optimum method and welding parameters. Weldability is studied over a range of material conditions, welding parameters, and directions. The influence of welding parameters on the fusion zone microstructure and resultant weldability is investigated using combination of microscopic examination and micro-hardness testing. This paper summarizes some of the results of a feasibility study conducted to understand the effects of welding parameters on localized microstructural features, cracking sensitivity, and mechanical properties of autogenously EB welded coupons of single crystal PWA1484.

Jan 1, 2004

By K. Yoo

Chalcopyrite is the most abundant copper sulfide mineral, which is normally processed using pyrometallurgical methods (i.e., smelting) to produce copper metal. Smelting has several major disadvantages, such as high gas-handling costs, high capital costs, saturation of sulfuric acid market, and inability to treat low-grade concentrates and to recover some by-products, such as zinc, nickel and cobalt. The development of hydrometallurgical processes for chalcopyrite is desirable to overcome the problems of smelting. Because chalcopyrite is refractory, the leaching rate for chalcopyrite is very low. Therefore, increasing the leaching rate has been extensively investigated, both in sulfate and chloride media, as well as in the presence of bacteria. Chloride leaching processes have shown relatively high leaching rates. The mechanism of the chloride leaching process has been investigated, but the behavior of chalcopyrite leaching in chloride solution is not clear. Therefore, the effect of the solution redox potential on the leaching rate of chalcopyrite in chloride solution was investigated. In the present study, leaching experiments were carried out using 0.1 M chloride solutions and the results indicate that high leaching rates of chalcopyrite can be achieved at relatively low solution redox potentials.

Jan 1, 2007

By B. Zhu, W. E. Lee, N. Li

Al powder is used extensively as an antioxidant in carbon-containing bricks, but it cannot be used directly in water-based carbon-containing castables due to its hydration tendency. To overcome this problem, in this work, SiO2-PVA (polyvinyl alcohol) inorganic-organic hybrid coatings have been prepared via sol-gel processing, and used to coat Al powder. The hydration behaviour of uncoated and coated Al powders has been investigated in water at 60 or 100°C for 36h by examining phase and microstructural changes. While significant hydration is detected in uncoated Al powder, no obvious hydration is detected in coated Al powder, indicating that its hydration resistance has been greatly improved. Oxidation resistance of graphite coexisting with uncoated or coated Al powder was also investigated in air at 1250°C for 1.5h. The oxidation ratio of graphite coexisting with coated Al powder was similar to that of graphite coexisting with uncoated Al powder, indicating that both powders showed similar antioxidising behaviour. This, along with the much improved hydration resistance, makes the coated Al powder a potential antioxidant in carbon-containing castables systems.

Jan 1, 2004

By M. Al-Hilal, G. Rajja, A. Al-Ali, Y. Jubeli

Abstract -A radiometric survey was carried out over clastic sediments in the immediate vicinity of some phosphatic sediments of Cretaceous age in the Wadi Qasser Al-Hallabat basin of central Syria. The objective was to explore for uranium and to define its dispersion pattern. This was based on ground radiometric surveys and geological studies. All ground surveys (using radon emanometry, track etching, gamma-ray survey and geochemistry) gave similar results, outlining the locations of the radioactive phosphatic formations in the basin, and indicating the dispersion pattern of uranium in the clastic sediments in the surrounding area. The dispersal of uranium from upper Cretaceous phosphatic formation occurs by mechanical weathering and chemical leaching by oxidizing surface waters. A rough estimate is that about one-third of the original uranium content of the Cretaceous sediments has been dispersed. Mechanical erosion is responsible for the main part of this released uranium, which now occurs in Recent sediments. However, the occurrences of spotty secondary U mineralization indicates that another small part of the available uranium must have been chemically leached out by the prevailing oxidizing waters, forming minor surficial minerals.

Jan 1, 1998

By V. Evans

Mine lateral development advance rates currently average about 5 metres (16.5 ft.) per day. Granduc Tunnel hit 35.1 metres (115 ft.) on their best day, 12 km from the portal, single heading forty-three years ago. This Canadian mining record remains an excellent example of rapid drill and blast excavation with suggestions for improving current practice.

May 1, 2011

By Richard Murphy

"The general geology of the Great Bear Lake area has been described by; D. F. Kidd in the Summary Report of the Geological Survey for 1932. A brief description of the Eldorado mine was prepared by C. S. Lord for Memoir 230; Mineral Industry of the Northwest Territories; published by the Geological Survey in 1941. Recently; a detailed geological examination of the mine area has been initiated by the Geological Survey and; under A. W. Jolliffe's leadershif; J. D. Bateman; H. B. Thurber; and M. Feniak have prepared a number of maps and reports; as yet unpublished. Detailed mapping of the mine has been carried out since August; 1943; by A. W. Esty.Kidd has shown that, in the largely granitic country along the east side of Great Bear lake, the Echo Bay district is one of several underlain by older rocks . These he has divided into the Echo Bay and Cameron Bay groups. The former are strongly altered sediments, .porphyries, and lavas; the latter and younger group is predominantly sedimentary and far less altered. Associated with the granite, which everywhere intrudes the sediments and volcanics, are earlier differentiates. Later than all these rocks are various basic intrusives, collectively termed diabase. All the rocks are of Precambrian age."

Jan 1, 1954

Falling asleep at the wheel of a moving vehicle is not only dangerous but avoidable. It is implicated in up to 30% of all road fatalities in general and up to 65% of mining incidents involving haulage trucks. These types of crashes normally result in serious injury and/or fatality due to the lack of breaking that occurs. However, when a 300 tonne haul truck has a sleep related crash it is not only the safety of the driver that has a high price but also the commercial impact on the mines? productivity and efficiency. We have been developing our ASTiD technology which stands for the Advisory System for Tired Drivers to seamlessly integrate in to Modular Mining?s Dispatch system to provide real-time early warning fatigue risk management. The benefits being driver shift optimisation, sustained productivity and of course less accidents. By monitoring the drivers alertness levels in real-time using ASTID, the Dispatcher becomes empowered to make critical, management decisions that will ultimately prevent serious injury or loss of life and the driver gets to stop when he needs to and not just when he is supposed to. This paper shows how this integrated solutions works.

May 1, 2011

By M. Gruber-Pretzler

Technical Sn- bronzes tend to form both macrosegregations and microsegrega¬tions during DC-casting due to the particular thermodynamic properties and kinetics of phase transformation. As a result a heterogeneous cast microstructure forms that is some¬times a reason for a decrease in workability. The extent of macrosegregations in DC-casting can effectively be influenced by casting parameters like casting velocity, primary cooling or inlet geometry which in fact change the relative flow between the melt and the forming solid. In order to understand the influence and interaction of the related phenom¬ena, simulation methods are applied. The solidification of the strand as well as the forma¬tion of macrosegregation are simulated with a two phase volume averaging model. The velocity field of the melt flow is explicitly calculated by solving the corresponding mo¬mentum conservation equations. Within the mushy zone the local formation of microseg¬regations in the presence of feeding flow is estimated. The thermodynamics of the Cu-Sn system is accounted for and it is distinguished explicitly between interface and average concentrations. To investigate the influence of feeding flow on the formation of mac-rosegregations, a study has been performed. Based on this result, the phenomena of mac¬rosegregations are described in a detailed discussion.

Jan 1, 2007

By Jeffrey D. Smith, William G. Fahrenholtz, Jose M. Soto

Interactions between A356 aluminum (Al-Si alloy) and dense fused silica (FS) riser tubes used for low-pressure casting of aluminum alloys were evaluated using a sessile drop approach. The tubes have a short service life, but cost and thermal shock resistance make them an effective solution. The main problem encountered during use is the reaction of aluminum with silica to form alumina and silicon, which causes failure. Tests have been conducted on as-fired (uncoated) and modified (coated) tubes. Experiments were carried out in a horizontal furnace at 1225°C under argon to minimize the effect of the aluminum oxide on the interactions at the alloy-silica interface. Images of the drop were acquired and contact angle values were estimated for uncoated and coated samples, but no significant differences in the contact angles were observed. Scanning electron microscopy revealed the presence of cracks at the interface between the reaction zone and the unreacted silica. The presence of reaction products (silicon in the reacting alloy and aluminum in a reaction zone between the alloy and the unaffected silica) has been confirmed using energy dispersive spectroscopy. A two layer coating system was found to be effective in reducing penetration of the aluminum alloy.

Jan 1, 2004

By S. C. Bouffard

Barrick&apos;s Zaldivar operation in Chile produces copper by heap leaching, solvent extraction, and electrowinning. The heap consists of a dynamic pad, and its stacking and operating conditions have changed over its 11 years of operation. These changes have included pad re-mining midway through the cycle, tightening of the irrigation drip lines, an increase of the coarseness of the particles, and an increase of the heap height. This paper reviews the heap operating data to understand the effects of these changes on the kinetics and recovery of copper minerals. Field tests demonstrated that neither re-mining nor tightening the irrigation grid added value for both low and high grade oxide and sulfide ores. The P80 of the feed ore was increased by 0.8 mm, which did not reduce the copper recovery of oxide and sulfide ores. The increase of the heap height above 8 m lowered moderately the copper recovery from sulfide minerals, and very slightly the recovery from oxide minerals. Despite the lower recovery, the higher tonnage stacked in the taller heap increased the copper output. Optimizing the chemistry of the agglomeration and feed solution holds more promise for increasing the copper recovery than the above physical changes.

Jan 1, 2007

By A. E. Dyment

In formulating an explosive for any specific set of conditions, various factors must be taken into consideration. Is it to be subjected to water or moisture? .If so, it must be designed to have an inherent ability to resist water. Is it to be used in confined spaces underground, where ventilation is limited? If it is, it must possess qualities enabling it to form, upon explosion, the minimum quantity of noxious gases, such as carbon monoxide or oxides of nitrogen. Is it for use where low temperatures may possibly prevail? If so, it must be capable of resisting such temperatures without freezing. Is it for use where dust or inflammable gases may be present? If it is, then it must be so formulated as to produce, upon detonation, a flame of the lowest possible temperature and the shortest possible duration, in order to lessen the chance of ignition of such gas or dust. This is actually the essential property of a permitted explosive, and it is undoubtedly the most important characteristic of an explosive which is to be used in gassy or closed-light mines. This being the quality that distinguishes permitted explosives from other types, it is interesting to investigate the ways and means by which the low-flame-temperature characteristic is obtained . Generally speaking, such explosives are so designed as to contain comparatively small quantities of nitroglycerin and relatively large quantities of the strength-producing salt, ammonium nitrate. This ingredient does not develop as high a temperature upon explosion as does nitroglycerin, so its presence, in large measure, in place of nitroglycerin results in an explosive which has an inherent low-flame-temperature characteristic, as opposed to one which is .made up largely of nitroglycerin, which would ordinarily be in the high-flame-temperature class. Additions are also made of flame-quenching salts such as sodium chloride, ammonium chloride, and up to a certain limiting percentage of sodium nitrate. These salts, with the exception of the last, do not ordinarily take an active part in the explosive reaction, being present primarily to absorb heat liberated by the reacting ingredients.

Jan 1, 1947